A large number of electrical devices (loads) having a relatively large rated power are mounted on an electric vehicle. Therefore, it is essential to configure, in the resonant inverter circuit included in the vehicle auxiliary power supply device, a protection function against overcurrent.
The idea behind conventional overcurrent protection in the resonant inverter circuit is generally to immediately turn off the switching element (hereinafter, described as “SW element”) when overcurrent is detected.
Although it is neither a technology related to the vehicle auxiliary power supply device nor a technology related to the resonant inverter circuit, the invention of Patent Literature 1 described below (name of the invention: current detection method in a resonant converter) discloses a technology in which when overcurrent is detected, the on-time of the SW element is reduced, thereby limiting the current flowing in the SW element and thus preventing the SW element from being destroyed (hereinafter, referred to as “element destruction”).